feat(agb02): gpio reader sketch

machines/agb02/_configuration.nix

@@ -3,6 +3,7 @@
 {
   imports = [
     "${modulesPath}/installer/sd-card/sd-image-aarch64.nix"
+    ./users.nix
   ];
   sdImage.compressImage = false;
   services = {
@@ -13,5 +14,10 @@
   networking.hostName = "agb02";
   networking.networkmanager.enable = true;
 
+  environment.systemPackages = [
+    (pkgs.callPackage ./agb {})
+    pkgs.libgpiod
+  ];
+
   system.stateVersion = "24.11";
 }

machines/agb02/agb/agb.cpp

@@ -0,0 +1,137 @@
+#include <curlpp/cURLpp.hpp>
+#include <gpiod.hpp>
+#include <iostream>
+#include <thread>
+
+using namespace std::literals::chrono_literals;
+
+constexpr std::chrono::microseconds debounce = 40ms;
+constexpr std::chrono::microseconds poll_period = 50ms;
+
+constexpr std::pair<double, double> joystick_movement(1.0, 1.0);
+
+const gpiod::line::offsets drive_down = { 21, 13, 6 };
+
+const gpiod::line::offsets decoder = { 0, 0, 0, 0, 0, 0, 0, 0 }; // lsbf
+const gpiod::line::offsets joystick = { 0, 0, 0, 0 }; // x+, y+, x-, y-
+const gpiod::line::offset black_button = 0;
+const gpiod::line::offset white_button = 0;
+
+const gpiod::line_settings input_settings =
+  gpiod::line_settings()
+    .set_direction(gpiod::line::direction::INPUT)
+    .set_bias(gpiod::line::bias::PULL_UP)
+    .set_active_low(true)
+    .set_debounce_period(debounce);
+
+// thanks to https://en.wikipedia.org/wiki/Gray_code#Converting_to_and_from_Gray_code
+inline uint8_t gray_to_binary(uint8_t num)
+{
+    num ^= num >> 4;
+    num ^= num >> 2;
+    num ^= num >> 1;
+    return num;
+}
+
+uint8_t read_decoder_realpos(gpiod::line_request& line_reader){
+  static gpiod::line::values decoder_read(8);
+  line_reader.get_values(decoder, decoder_read);
+  uint8_t graycode = 0;
+  for(uint8_t i = 0; i < 8; ++i) graycode |= uint8_t(decoder_read[i]) << i;
+  return gray_to_binary(graycode);
+};
+
+inline void clamp_decoder(uint8_t& decoder, int move){
+  decoder = uint8_t(std::clamp(decoder + move, 0, 255));
+}
+
+int main(const int argc, char const* const* const argv) {
+  if(argc < 2)
+    return 1;
+
+  /// init gpio chip ///
+
+  gpiod::chip chip(argv[1]);
+  gpiod::line_request line_reader =
+    chip.prepare_request()
+      .set_consumer("AGB")
+      .add_line_settings(drive_down,
+        gpiod::line_settings()
+          .set_direction(gpiod::line::direction::OUTPUT)
+          .set_drive(gpiod::line::drive::OPEN_DRAIN)
+          .set_output_value(gpiod::line::value::INACTIVE)
+      )
+      .add_line_settings({ black_button, white_button }, input_settings)
+      .add_line_settings(joystick, input_settings)
+      .add_line_settings(decoder, input_settings)
+      .do_request();
+
+  // let the settings apply
+  std::this_thread::sleep_for(poll_period);
+
+  /// init server communication ///
+
+  cURLpp::initialize();
+
+  /// internal state ///
+
+  gpiod::line::values joystick_read(4);
+  std::pair<double, double> spot_pos(0.0, 0.0); //TODO: init from server
+
+  uint8_t decoder_pos = 0; //TODO: init from server
+  uint8_t decoder_realpos = read_decoder_realpos(line_reader);
+
+  bool white_pressed = false;
+  bool black_pressed = false;
+
+
+
+
+  for(;;){
+    std::this_thread::sleep_for(poll_period);
+
+    /// joystick ///
+    line_reader.get_values(joystick, joystick_read);
+
+    if(bool(joystick_read[0])) spot_pos.first  += joystick_movement.first;
+    if(bool(joystick_read[1])) spot_pos.second += joystick_movement.second;
+    if(bool(joystick_read[2])) spot_pos.first  -= joystick_movement.first;
+    if(bool(joystick_read[3])) spot_pos.second -= joystick_movement.second;
+
+    if (bool(joystick_read[0]) || bool(joystick_read[1])
+        || bool(joystick_read[2]) || bool(joystick_read[3]))
+      ; //TODO: send to server
+
+    /// Buttons ///
+    bool pressed = bool(line_reader.get_value(black_button));
+    if(pressed ^ black_pressed)
+      ; //TODO: send to server
+    black_pressed = pressed;
+
+    pressed = bool(line_reader.get_value(white_button));
+    if(pressed ^ white_pressed)
+      ; //TODO: send to server
+    white_pressed = pressed;
+
+    /// decoder ///
+    uint8_t new_realpos = read_decoder_realpos(line_reader);
+    uint8_t seen_travel = std::abs(int(new_realpos) - int(decoder_realpos));
+
+    //TODO: check CW and CCW
+
+    // CW
+    if(seen_travel < 50 && new_realpos < decoder_realpos)
+      clamp_decoder(decoder_pos, seen_travel);
+    if(seen_travel >= 50 && new_realpos > decoder_realpos)
+      clamp_decoder(decoder_pos, 256 - seen_travel);
+
+    // CCW
+    if(seen_travel < 50 && new_realpos > decoder_realpos)
+      clamp_decoder(decoder_pos, -seen_travel);
+    if(seen_travel >= 50 && new_realpos < decoder_realpos)
+      clamp_decoder(decoder_pos, seen_travel - 256);
+
+    if(seen_travel)
+      ; //TODO: send to server
+  }
+}

machines/agb02/agb/default.nix

@@ -0,0 +1,17 @@
+{ stdenv, libgpiod, curlpp, curl }:
+stdenv.mkDerivation rec {
+  pname = "agb";
+  version = "oct-24";
+  src = ./.;
+
+  buildPhase = ''
+    g++ --std=c++23 agb.cpp -o agb \
+      -L${libgpiod}/lib -lgpiodcxx -I${libgpiod}/include \
+      -L${curl.out}/lib -lcurl -I${curl.dev}/include \
+      -L${curlpp}/lib -lcurlpp -I${curlpp}/include
+  '';
+  installPhase = ''
+    mkdir -p $out/bin
+    cp agb $out/bin
+  '';
+}